The present invention relates to stabilizer compositions based on monoalkyl glycerol ethers and aromatic alcohols and use thereof.
Stabilizer compositions are used in many aqueous systems in order to control microbial growth. An important field of use is cosmetic formulations, such as creams, lotions, sunscreen products, shampoos, shower gels and bathing additives. Stabilizer compositions can also be used in cleaning, care and hygiene products for the home (e.g. hand washing preparations), and in many technical sectors, e.g. in cutting fluids, diesel fuels, paints and coatings.
There continues to be a great need for improved compositions which have a broad spectrum of activity towards bacteria, yeasts, moulds and viruses, develop their biocidal effectiveness (killing of microorganisms) under conditions met in practice even at low use concentrations and—particularly in the case of cosmetic and pharmaceutical preparations—are highly physiologically compatible.
It is known that glycerol monoalkyl ethers have or support antimicrobial effects. Of particular suitability is 1-(2-ethylhexyl) glycerol ether, which is available under the trade name Sensiva® SC 50 (Schülke & Mayr GmbH, Germany). However, glycerol monoalkyl ethers on their own do not have a broad spectrum of activity towards gram-positive and gram-negative bacteria, fungi, yeasts and viruses, as is necessary in specific dermatological preparations, such as, for example, skin antiseptics.
DE 42 40 674 C2 relates to deodorizing glycerol monoalkyl ethers, the 2-ethylhexyl group being specified as the alkyl group. The monoalkyl glycerol ethers can be used in combination with one or more other deodorizing substances, specifically suitable deodorizing substances being, for example, phenoxyethanol and phenethyl alcohol.
DE-A-40 26 756 discloses a preservative which comprises a mixture of a) organic acid, b) aromatic alcohol and c) guanidine derivative, where the presence of d) substituted glycerol ether is optionally possible. Example 11 discloses a mixture of, inter alia, phenoxyethanol, phenoxybutanol and 3-octyloxypropane-1-2-diol.
DE-A-41 24 664 discloses mixtures of (A) arylalkanol with diol as preservative, where glycerol monoalkyl ethers are intended as diols. DE-A-100 28 638 relates to storage-stable compositions of glycerol monoalkyl ethers which, as well as comprising glycerol monoalkyl ether and antioxidant, can also comprise additives such as benzyl alcohol, phenyl alkanol.
DE-A-100 25 123 relates to cosmetic deodorants which comprise an active ingredient combination which comprises (I) one or more substances chosen from the group of mono- and oligoglycerol monocarboxylic acid monoesters, (II) one or more aryl compounds and (III) one or more glycerol ethers. Preferred aryl compounds are chosen from the group consisting of phenoxyethanol, anis alcohol, 2-methyl-5-phenylpentan-1-ol and 2-methyl-4-phenylbutan-2-ol. DE-A-100 25 124 relates to preparations with a content of a combination of (A) an active ingredient or two or more active ingredients chosen from the group of glycerol monoalkyl ethers and (B) an active ingredient or two or more active ingredients chosen from the group of aryl-substituted alcohols.
The application DE 102 24 979, filed by the applicant and published subsequently, relates to synergistic preparations based on mixtures of glycerol ethers with aromatic alcohol for controlling mycobacteria. A disinfectant is described which comprises (a) alkyl glycerol ether and (b) one or more aromatic alcohols.
However, a disadvantage of combinations of monoalkyl glycerol ethers with aromatic alcohol has now been found to be that the combinations do not always have reliable protection when incorporated into water-based products. This is attributable, inter alia, to the fact that, on the one hand, both monoalkyl glycerol ethers and aromatic alcohols have limited solubility in water and, on the other hand, certain maximum concentrations must not be exceeded.
For example, the Cosmetics Directive (dated Jun. 14, 2000, BGB1 I, p. 846, Annex 6, Part A) stipulates certain maximum concentrations (e.g. benzyl alcohol maximum 1.0% by weight, phenoxyethanol maximum 1.0% by weight, 1-phenoxy-2-propanol maximum 1.0% by weight). Furthermore, due to the limited solubility in water of glycerol monoalkyl ethers and aromatic alcohols, certain mixing ratios of the combination with water are excluded, for which reason preferred concentrates of the prior art are anhydrous.
Thus, in numerous cosmetic bases, combinations of monoalkyl glycerol ethers with aromatic alcohol do not achieve adequate protection against microbial growth if the physically possible or permissible amount of the constituents is used: the limited solubility is an obstacle to increasing the use concentration, and in addition permissible maximum concentrations would then be exceeded. Stabilizer compositions should, however, be able to be used as diversely as possible, thus both be able to be incorporated into aqueous solutions to form clear mixtures, and also to be reliably effective in possibly ointment-like cosmetic products while observing the permissible maximum concentration.
Although it would be possible to include conventional active ingredients in the formulation in order to further increase the effectiveness of combinations of glycerol monoalkyl ether and aromatic alcohol, numerous conventional active ingredient have disadvantages. Thus, for example, an oestrogenic effect or an endocrinal potential of phenols and parabens has been reported. Organohalogen compounds, such as iodopropynyl butylcarbamate, dibromodicyanobutane and 2-bromo-2-nitro-1,3-propanediol are not adequately environmentally compatible. Formaldehyde and formaldehyde donor compounds are suspected of being carcinogenic, and carboxylic acids, such as sorbic acid, are only effective at pH values less than 6 and can lead to discolorations. In addition, the use of such conventional active ingredients may lead to incompatibilities in the stabilized product or, in the case of application of the product, for example a cosmetic and/or pharmaceutical product, to allergic reactions.